This invention relates to augmentors, and more particularly, to augmentor flameholders.
Augmentors are used to increase thrust in gas turbine engines including core engines and bypass ducts. Augmentors typically include an exhaust casing and liner therein which defines a combustion zone. Fuel spraybars and flameholders are mounted within the augmentor and introduce fuel to the combustion zone for igniting to increase thrust from the gas turbine engine.
Various types of flameholders are known and augmentors typically include a plurality of radial and circumferential flameholders. Such flameholders include V-shaped gutters used for sustaining combustion during gas turbine engine reheat operations. The radial flameholders intersect the circumferential flameholders and form a radial cap which extends circumferentially around the augmentor.
During operation, hot combustion gases exit the core engine and are mixed with airflow exiting the bypass ducts. Fuel is introduced to the mixture and the fuel/air mixture is ignited producing hot combustion gases used for thrust. Hot combustion gases may travel radially outward through the augmentor radial flameholders and impinge upon the radial cap. As a result of hot combustion gases, thermal distress develops within the radial cap which reduces the useful life of the flameholders. Specifically, because of the exposure to the hot combustion gases, the radial cap may experience thermal creep and erosion. Furthermore, because of cooler air introduced to the augmentor from the bypass ducts, thermal gradients develop within the flameholders which often lead to LCF cracking at trailing edges of the flameholders.
In an exemplary embodiment, an augmenter for a gas turbine engine includes an insert to reduce potential thermal stresses caused by hot combustion gases impinging components within the augmentor. The augmentor also includes a plurality of radial flameholder gutters and at least one outer circumferential flameholder connected to the radial flameholders to form a radial cap. The radial cap includes an upper and lower surface and extends circumferentially within the augmentor. The insert is contoured to conform to the radial cap. The insert is attached to the radial cap and includes a top surface, a bottom surface, and a plurality of openings extending therebetween. The openings permit the insert to be attached to the radial cap.
As the gas turbine is operated, the augmentor is exposed to airflows exiting a core engine and bypass ducts. Hot combustion gases exiting the core engine flow radially outward along the radial flameholders towards the radial cap. The insert prevents the hot combustion gases from impinging on the radial cap. As a result, thermal creep and erosion within the radial cap are reduced. Furthermore, because the insert extends further downstream than the circumferential flameholders, cracking at circumferential flameholder downstream edges due to low cycle fatigue, LCF, is reduced.